So I was born and was a baby for a while. You see the thing is Asgardians age VERY slowly even as babies at least in the MCU. Now that matters because I had to stay as a child for a while . It was a bit awkward sure but otherwise fine. Most of my babyhood was spent mediating . I was also introduced to Loki as well and we were crib neighbors.
A good news was that meditating paid of.
[ Ding due to constant meditation user has awakened psychic potential
Ding due to awakening psychic potential+1% Template synchronization
Ding user has become a psionic nexus due to synchronization]
Suffice to say that I was meditating whenever possible . I was also trying to experiment with cosmic energy whenever possible . Now of course I eventually learned to use telepathy so I was practicing it to peak into others minds and learn stuff whenever possible. Asgardian parenting is also certainly odd cause Frigga literally took me to war when Asgard and Joutenhiem were duking it out .
Loki was also a bit of a nuisance because of what I already know of his character I made it a habit to always keep an eye on his mind. That stopped most of the pranks before they could begin. Anyway most of my childhood was spent on training and learning how to be a warrior from Odin. I made sure no one knew about my use of phoenix force powers with judicious use of telepathy mostly because I wanted everyone to think of me as a warrior more then a sorcerer to have some face as the Chinese would say. Smart folks those guy if a bit too obsessed with honor.
By the time I completely synchronized with the phoenix force template it was already my coronation aka the start of Thor 1.